I've send an email to one professor at every school I am applying; I think it is a good idea to initiate a contact, show them you are interested in their research, and most importantly I wanted to know if their research group was already full or not. Only one professor never wrote me back (he was indeed way out of my league...) but all the other (including quite a few big shots) wrote me back. Most professors wrote a very generic email in which they encourage me to apply at their school, they told me they will look for my name once the application process start and they ask me to recontact them once I'm in. Of course, I don't think that those professors will actually think my profile is any better because I contacted them. But, some professors actually showed much more interest and we've exchanged quite a few emails. The bottom line, I do think it helps quite a bit if you can actually initiate a discussion with a professor (but I'm not sure since I'm applying this season as well), but that's pretty hard. Especially near the application season when they are very busy. I think the best is to contact them in the summer, but then chances are they will forget about you.